Thats a good point and i pretty much do have everything just seems like an extremely daunting task to treat them all mostly because i dont think id be able to get them out without removing the entire rockscape aswell but it is definitely better to be prepared just incase.It sounds like you have everything you need. I'd get started right away as you need time to get your salinity and temp right, and that can take a day or two.
My position is based on a personal experience of a few weeks ago, where I lost a fish in QT. A timely water change would have saved the fish, but I had nothing ready.
Your better off anticipating the worst case scenario and not needing it.
If it is something i can treat with prazi or metro or anything reef safe i would probably just do an in tank treatment but i guess i could get one of the 30g pre-emptively filled with the 30ppm ro water and get it heated and everything aswell so i dont have to wait for hours or days to fill and reach temp if i do need it. Thanks for the suggestion. Not sure how i would even treat them all though when i cant really figure out what is going on with the clown. Sorry for your recent loss aswell. I am hesitant to add salt if i do fill one since i dont know if i will forsure use it or what levels i would need to make it to without knowing the specific disease though and it only takes like a few hours to mix to be safe to use for fish in a pinch aslong as i move some cycled filter material, add bottle bacteria, and have water made and heated.